Mechanisms of light field modulation in parameter-tuned cascaded microcavity optical tweezers and particle sorting study

By tuning cascaded microcavity length and orifice dimensions, this study reveals a light-field modulation mechanism in microcavity optical tweezers, where parameter-optimized configurations (include Field Uniformity and Energy Transfer Efficiency) generate tunable optical gradients at the orifice. Results demonstrate that choosing a microcavity of an appropriate size can enable the light force to dominate at the aperture, supplemented by fluidic force, and generate a more uniform light field. Under these conditions, size-matched particles overcome the optical trapping constraints at the aperture and are captured within the microcavity under the influence of fluidic forces from surrounding weak optical force regions, while other particles are repelled. This achieves particle size sorting. The work clarifies microcavity parameter-dependent optical-hydrodynamic coupling and establishes a synergistic multi-physics manipulation strategy, advancing applications in single-cell sorting and nanodrug screening.